ZR-1 Street Skinner

[Paul Workman]

Originally Posted by tcz062

Question, why does it not matter 2 or 4 bolt ? The 4 bolt mains were stronger bottom end ? Is that not why L82's are more disreable than L48's ? Getting educated so I can make the correct decision on my offer.

To think of the "two bolt mains" in LT5 in the context of a SBC is "apples to oranges". In the first place, the main bearing caps of a SBC stand alone as individual pieces, held by 2 or 4 bolts achored in the block.

The LT5's main caps are moulded into a separate girdle or "ladder". The head bolts for a "two bolt" 90 LT5 are huge - approx. a foot or so long - and together weigh over 20#!!

The bolts do double duty. They sandwich the block between the heads and the a girdle (ladder-like) section into which the main caps are mouled. Thus thrust on the heads is directly transferred to clamping force of that girdle (and with it, the main caps) to the block - a truly inspired engineering concept.

The four-bolt LT5 block has auxillary bolts that are short and anchor into the block itself (vis-a-vis SBC method) - part of the 405 hp upgrade "to better stabilize the main caps" (Heart Of The Beast). Both the long head bolts AND the short aux. bolts are smaller in diameter than the 2-bolt motor's bolts (Marc Haibeck explained in a post over a year ago). But, as far as strength goes, (again from Marc) there's really little practical advantage in terms of reliability or other apparent advantage between the 2 vs 4 bolts.

Case in point, There are a few 427 & 441 cid 2-bolt, 10-second cars roaming the country that are making around 700 chp and turning over 7500+ rpm with no problems. So, again, the SBC and LT5 in the context of two vs. four bolt mains have no comparisons, and both LT5 motors can be upgraded to big hp w/o the kind of concerns one would have with a SBC upgrade. Except for cases where the LT5 has been "sprayed" too much, the bottom ends don't break (apparently).

Anywayz... 2 vs. 4 bolt is apparently NOT a practical issue in actual use/practice, mechanically speaking.

P.